Here, Here. This is a phenomenom not solely found in R.I. . I've been noticing and stumbling over this detritus since I've started fishing several years ago. Its kind of funny as these people want to get out in the clean air and enjoy some good clean fun but leave a dump site when they're done.
Its only getting worse. Apart from the beer cans and bait boxes I usually wind up picking up several miles of line in a season. The only good thing I can say is there is some surprises every once in awhile amongst the trash. Spinning reel, several pounds of lead, hooks, leaders and to date about $60 in plugs.
You are right though if this keeps up many areas may be closed to fisherman because of the ill will spread by the slobs. Again the adage a few bad apples will spoil the whole.
Fed up and disgusted on PI
Mike D